The invention relates to a method of tuning a belt drive system, more particularly, to a method of tuning a belt drive system vibration by using a tensioner having a damping rate on an accessory belt tight side and a tensioner having a damping rate on an accessory belt slack side to tune a system vibration.
Mechanical tensioners are widely used in automobile engines to control belt tensions of accessory belt drives. Friction damping, force or torque, is usually utilized in a tensioner to control tensioner arm motion and vibration of the belt drive system. A belt drive with a high vibration level will require high damping from the tensioner to prevent belt slip, noise, span vibration, as well as other noise, vibration and harshness problems. However, the friction damping of a tensioner has a certain limitation dictated by system requirements, tensioner tension, belt life and tensioner size. Because of the tensioner""s limit of friction damping, there are some IC engines where a mechanical tensioner alone is not capable of properly controlling belt tensions and consequently they are unable to eliminate vibration and noise problems from a belt drive.
Other tensioners are available that comprise two pulleys that simultaneously engage a belt, but they do not tune a system vibration.
Representative of the art is U.S. Pat. No. 4,416,647 (1997) to White which discloses a belt tensioner having a pulley simultaneously engaging a belt tight side and a belt slack side on either side of a driven accessory. The pulleys are connected to an arm. The arm is pivotally connected to a surface at a single pivot point.
Also representative of the art is U.S. Pat. No. 4,981,116 (1991) to Trinquard which discloses an apparatus for wrapping a belt more than 180 degrees around a wheel of an engine. The device teaches reducing the amplitude of the variations of tension in a belt under extreme conditions. Only one of the pulleys is pivotably mounted to a lever.
What is needed is a belt drive system having two tensioners for tuning a system vibration. What is needed is a belt drive system tuned by using a tensioner having a damping rate on an accessory belt tight side and a tensioner having a damping rate on an accessory belt slack side. What is needed is a belt drive system tuned by using a tensioner having a damping rate on an accessory belt tight side and a tensioner having a damping rate on an accessory belt slack side wherein the accessory has a highest effective inertia as compared to other system components. What is needed is a belt drive system tuned by using a tensioner having a damping rate on an accessory belt tight side and a tensioner having a damping rate on an accessory belt slack side wherein each tensioner is joined by a biasing member. The present invention meets these needs.
The primary aspect of the invention is to provide a belt drive system having two tensioners for tuning a system vibration.
Another aspect of the invention is to provide a belt drive system tuned by using a tensioner on an accessory belt tight side and a tensioner on an accessory belt slack side.
Another aspect of the invention is to provide a belt drive system tuned by using a tensioner on an accessory belt tight side and a tensioner on an accessory belt slack side wherein the accessory has a highest effective inertia as compared to other system components.
Another aspect of the invention is to provide a belt drive system tuned by using a tensioner on an accessory belt tight side and a tensioner on an accessory belt slack side wherein each tensioner is joined by a biasing member.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises a method of using tensioners to tune a belt drive system. A tensioner having a damping rate is used on an accessory belt slack side and a tensioner having a having a damping rate is used on an accessory belt tight side. Outside of a predetermined engine speed range, the tight side tensioner arm does not move because the dynamic tension in the span is less than the tight side tensioner friction damping. Within a predetermined engine speed range the tight side tensioner arm moves in order to damp a belt drive system vibration.